甲基化酶NSUN2介导的TGFB1 mRNA-m5C修饰激活TGF-β信号通路促进肾癌转移的机制研究

肿瘤转移是癌症致死的主要原因。mRNA m5C修饰调控RNA稳定性和翻译，其在肿瘤转移中的作用及机制尚不明确。我们发现：mRNA m5C水平和m5C相关蛋白NSUN2/YBX1在肾癌组织及其转移灶中上调，其表达与患者预后负相关；敲除NSUN2/YBX1抑制肾癌细胞体外迁移和体内转移；敲除NSUN2降低TGFB1 mRNA的m5C水平及其稳定性；敲除NSUN2/YBX1抑制TGFB1表达和TGF-β信号通路。据此提出假说：NSUN2提高TGFB1 mRNA的m5C水平，在YBX1的介导下增强TGFB1的mRNA稳定性，进而激活TGF-β信号通路以及促进肾癌转移。本项目拟采用基因敲除、转录组和甲基化组测序等方法，结合体内外模型和临床标本，阐明NSUN2/YBX1介导的mRNA m5C修饰紊乱在肾癌转移中的功能及其机制，为m5C通路作为高危肾癌患者术后降低复发转移的辅助治疗靶点提供理论依据。

Metastasis is the foremost cause of cancer-related death. mRNA 5-methylcytosine (m5C) regulates the stability and translation of mRNAs, the roles of which in tumor metastasis and the underlying mechanism remain unknown. We found that the levels of mRNA m5C and NSUN2/YBX1 were upregulated in human renal cell carcinoma (RCC) and metastatic tissues and were inversely correlated with prognosis of RCC. Knockout of NSUN2/YBX1 inhibited in vitro migration and in vivo metastasis of RCC cells. The levels of TGFB1 mRNA m5C and the mRNA stability of TGFB1 were significantly decreased by NSUN2/YBX1 knockout. In addition, Knockout of NSUN2/YBX1 reduced the expression of TGFB1 and repressed the TGF-β signaling pathway. Therefore, we hypothesized that NSUN2 increased the level of TGFB1 mRNA m5C, and then enhanced the YBX1-mediated mRNA stability of TGFB1 to activate the TGF-β signaling pathway, resulting in the promotion of RCC metastasis. Based on these preliminary findings, we will perform biological experiments including gene knockout, RNA-Seq and m5C-Bis-Seq, and combine in vitro and in vivo models as well as clinical samples, to disclose the roles and the underlying mechanism of NSUN2/YBX1 mediated deregulation of mRNA m5C in RCC metastasis. Our results will provide theoretical basis for m5C pathway as a potential target for the treatment of high-risk RCC patients to reduce relapse and metastasis.